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SubjectRe: copy_from_user() fix
On Tue, 25 Aug 1998, Jamie Lokier wrote:

> I bet no applications at all currently check for EFAULT from system
> calls, unless they're really weird and are doing it to behave _as if_
> they'd received SIGSEGV. Actually I bet they don't bother because every
> syscall would need to be wrapped. I'm theorising that this could screw
> up Wine in some unusual but valid cases.

I'll take your money. You prove that there are *no* applications
that check for EFAULT and I'll pay up. Otherwise you pay up. Just
one condition - we set a time limit :-).

Seriously though, having looked at good knows how many iBCS traces
I can tell you that there is plenty of code out there that assumes
the kernel will give error codes if something is wrong - even when
they don't explicitly check *what* error occurred. I'm willing to
bet some of it is EFAULT sensitive.

(There is code that depends on the *order* that things are checked
too - even though there is no standard for it)

> - Only a few applications care whether SIGSEGV is raised or not.

If you can say that for certain you have spent more on source licenses
than Bill Gates is worth!

> I propose EFAULT should be retained, but faulting syscalls should _also_
> raise SIGSEGV.

Nononono... If you *must* break compatibility with exisiting systems
so casually make it a personality flag. Preferably one that is off
by default unless an application *specifically* asks for it.

Mike

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